Observation of Antiferromagnetic Magnon Pseudospin Dynamics and the Hanle effect*

The quantized spin excitations of an antiferromagnet can be described as pairs of spin-up and -down magnons and characterized by a magnonic pseudospin. Here, we report experiments demonstrating control of magnon spin transport and pseudospin dynamics in a 15 nm thin film of the antiferromagnetic insulator hematite (α-Fe₂O₃) utilizing two Pt strips for all-electrical magnon injection and detection [1]. We observe an oscillation in polarity of the magnon spin signal at the detector as a function of the externally applied magnetic field. We quantitatively explain our experiments in terms of diffusive magnon transport. In particular, we observe a coherent precession of the magnon pseudospin caused by the easy-plane anisotropy and the Dzyaloshinskii-Moriya interaction. This observation can be viewed as the magnonic analogue of the electronic Hanle effect and the Datta-Das transistor, unlocking the high potential of antiferromagnetic magnonics towards the realization of electronics-inspired phenomena.
[1] Wimmer et al., arXiv 2008.00440 (2020).